[PATCH 4.9 11/12] scsi: sg: reset res_in_use after unlinking reserved array

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hannes Reinecke <hare@suse.de>

commit e791ce27c3f6a1d3c746fd6a8f8e36c9540ec6f9 upstream.

Once the reserved page array is unused we can reset the 'res_in_use'
state; here we can do a lazy update without holding the mutex as we only
need to check against concurrent access, not concurrent release.

[mkp: checkpatch]

Fixes: 1bc0eb044615 ("scsi: sg: protect accesses to 'reserved' page array")
Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Todd Poynor <toddpoynor@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/scsi/sg.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -2042,6 +2042,8 @@ sg_unlink_reserve(Sg_fd * sfp, Sg_reques
 	req_schp->sglist_len = 0;
 	sfp->save_scat_len = 0;
 	srp->res_used = 0;
+	/* Called without mutex lock to avoid deadlock */
+	sfp->res_in_use = 0;
 }
 
 static Sg_request *